I. Field of the Invention
The invention concerns itself with type carriers used in the selection of type symbols in photocomposing machines. Specifically, the invention deals with type carriers which can be clipped to a rotary cylindrical carrier roll, and more specifically with the case where several such type carriers, containing different groups of type symbols and/or code information, are sequentially arranged around the circumference of the cylindrical carrier roll.
II. Description of the Prior Art
Such type carriers are already known (DT-OS2,242,308) West German Patent No. This type of carrier roll for type symbols consists of an arrangement in which several segments are rigidly fixed by screws to the peripheral surface of a disk, each segment containing a group of type symbols or the like. The group of type symbols is adhesively fixed to the outer periphery of the individual rigid carrier segments in the form of a film. As in the case of most of the other photo composing machines known to the art, which work at high composing rates, the machine in question for this invention also is based on the principle that the type setting of the respective type symbol is done by means of a corresponding arrangement of optical elements onto a light sensitive layer while the carrier roll is in motion. To this effect, the cylindrical or disk-like carrier roll is in continuous motion at a relatively high rate of speed, and a flash illumination source is set off at that instant when the desired type symbol, or whatever, passes through the reproduction optics. Exposure is for such a short period of time that the continuing motion of the type symbol can be neglected.
The use of rigid segments as type carriers which can be fastened by means of screws onto a disk or another circular supporting device has the considerable advantage that they can be fastened to the carrier in such a manner that, even for high rates of revolutions and the centrifugal forces arising from this, they are not subject to slipping or other deformation effects; this makes it possible to avoid any of the reproduction flaws otherwise caused by these circumstances. The disadvantages of this design known to the state of the art, however, are that the film which is adhesively fixed to the outside surface of the individual segments, and which carries the type symbols, can easily be damaged by mechanical action. In addition, for a multiplicity of different types, as they are a necessity for photocomposing machines which are to be used at high rates of efficiency, a large stock of cylindrical segments is required, taking up considerable storage space.
Apart from the possibility of building a cylindrical type carrier composite from sequentially arranged rigid segments, it is also known in the art to use a respective cylinder to which filmstrips are clipped. For instance, a matrix-strip on a carrier frame of a photocomposition machine is known to the art (DTOS 2 246 603) West German Patent No. In this case guide openings are provided on the carrier frame for attaching the matrix-strip, and negative matrix-symbols and negative time slots are arranged opposite of each other on the opposing sides of the matrix-strip in certain spatial relationships to each other, and one end of the matrix-strip can be suspended from one end of the carrier frame, while the other end is provided with openings into which a spring element on the carrier frame can enter for the purpose of securing this end to the carrier frame.
It is a salient feature of this arrangement that the matrix-strip is again located on the outer peripheral surface of a disk or cylinder, and that, given a high loading force in the spring element, such a unit is difficult to manipulate and to install, or, should the spring tension be suitably redirected for easy handling, the danger exists that slippage or dislocation of the matrix-strip would occur during rapid rotation of the cylinder because of the centrifugal forces generated. Apart from the installation difficulties, and the reduced precision in setting type due to centrifugal forces, for the known device the exact alignment in mounting suffers on frequent use. Finally, temperature variations inside and outside the photocomposition machine may cause changes in the filmstrips employed.
In addition, a photocomposition machine is known which features a symbol-carrying matrix, a flash-exposure system to illuminate the symbols, and an optical system for projecting type onto an image surface (DT-OS 2024366) West German Patent No., in which the type carrier consists of film which has been clamped between rigid arc-shaped frames, which themselves are fastened to a cylindrical carrier. Again, this type carrier arrangement is subject to a lack of precision in the composing of individual symbols due to position changes caused by centrifugal forces. Changes in the dimensional tolerance factors caused by repeated mountings lead to deteriorations in the alignments. In addition, there is the consideration that film as such, when employed as carrier for the type symbols, hardly can result in high quality type setting, and that the unavoidable static charging of the film will result in soiling of the type symbols, even after relatively short usage. This soiling quickly becomes apparent in the projected picture or even the final product.
Thus, the requirements made for the type of photocomposing machine here under discussion, i.e., to have available a large number of intermingled, different type symbols for one composing process; to be able to project these onto a light-sensitive film in as short as possible a time, using a continuously rotating type carrier and a flash-illumination source, and to do so at very high composing quality standards. These requirements are indeed not completely met by the devices heretofore known to the art, or if so, are only met while accepting other disadvantages. The same is also true for the case of designs which allow for a relatively fast and simple exchanging of individual type carrier elements on a supporting device, which upholds the alignment requirements during repeated usage.
The same also holds for a further type carrier cylinder (DTAS 1 945 552) West German Patent No., on which each letter or each symbol can be singly mounted in an interchangeable manner. The individual type carriers are provided with a permanent magnet on their front side and can be made to stick to corresponding rings at the edge of the cylinder on any given spot of the periphery. In this design, the cylinder surface is provided with uniform perforations on several peripheral locations and in several tiers above each other; this for the purpose of allowing the projected light to pass and providing the necessary code information. The rings are fastened to striker bars, which again are fastened by screws to support elements on the cylinder.
When part of the type carrier elements are to be exchanged as a unit, it is necessary to disassemble the striker bar with the type elements immediately attached to it by removing the screws. The type carrier elements located in the immediately adjoining row thereby lose their second support surface, since the removed striker bar with its ring and the attached type carrier elements simultaneously double as the support surface for the second row of type carrier elements in the next row. The type carrier elements must be disengaged individually and at significant expenditure of time from the striker support plate, only to be replaced by others. Even the changing of the type carriers on the cylinder requires a considerable expenditure of time, since one set of type symbols includes as many as 120 individual characters. For the case where several type carrier segments are removed from one side of the cylinder, an imbalance is created in the cylinder, which in turn puts a considerable load on the bearings and the drive mechanism. Also, the magnets used in the described design are quite sensitive to shock. Metallic dust on the permanent magnets of the type symbol carriers does allow for the possibility of improper alignment.
Each individual type carrier element must be kept clean to achieve sharp images, since soiling occurs relatively quickly by static charging. The bilateral cleaning of hundreds of type elements is very time consuming.